虚拟存储管理器的页面调度
请求分页式存储管理：每访问一个地址时，首先要计算该地址所在的页的页号，然后查页表，判断该页是否在主存；如果该页不在主存且内存块未满，则调入该页；如果该页不在主存且内存块已满，则按页面淘汰算法淘汰一页后调入所需的页。 设该作业共有320条指令，即它的地址空间为32页，目前它的所有页面都还未调入内存。在模拟过程中，每访问一个地址时，首先要计算该地址所在的页的页号，然后查页表，判断该页是否在主存——如果该页已在主存，则打印内存块情况；如果该页不在主存且内存块未满，则调入一页并打印内存块情况；如果该页不在主存且内存块已满，则按页面淘汰算法淘汰一页后调入所需的页，打印内存块情况； 逐个地址访问，直到所有地址访问完毕。在所有320条指令执行完毕后，请计算并显示作业运行过程中发生的缺页率。 置换算法：请分别考虑FIFO和LRU算法。
首先设计指令类，代码如下:
package 页面调度;
import java.util.Random;
public class Order {
private int order; //指令内容
private int address; //指令地址
private boolean flag = false; //状态位，判断是否被访问
public Order() {
Random r = new Random();
this.order = r.nextInt(320);
this.address = this.order / 10 +1;
}
public boolean isFlag() {
return flag;
}
public void setFlag(boolean flag) {
this.flag = flag;
}
public int getOrder() {
return order;
}
public int getAddress() {
return address;
}
public void Print(){
System.out.println(" "+this.order+" "+this.address+" "+this.flag);
}
}然后构造页面类，代码如下：
package 页面调度;
import java.util.ArrayList;
public class Page {
private ArrayList<Order> page = new ArrayList<Order>(); //页面 数组
private int Number; //页面个数
public Page(int number) {
Number = number;
int count = 0;
while( count != number){
Order myorder = new Order();
if (this.IsExited(myorder.getAddress()) == false){
page.add(myorder);
count++;
}
}
}
public boolean IsExited(int order){
boolean flag = false;
if ( this.getPage().size() == 0){
flag = false;
}else{
for ( int i = 0 ; i < this.getPage().size() ; i++){
if ( this.getPage().get(i).getOrder() == order){
flag = true;
break;
}
}
}
return flag;
}
public ArrayList<Order> getPage() {
return page;
}
public int getNumber() {
return Number;
}
public ArrayList<Order> VisitOrderAlgorithm(){ //随机访问页面算法
ArrayList<Order> myorder = new ArrayList<Order>(); //随机获取的页面数组
int count = 0;
while( count != 3){
int i = 0;
do{
if ( this.IsALLVisited() == false){
if ( this.page.get(i).isFlag() == false){
myorder.add(this.page.get(i));
this.page.get(i).setFlag(true);
break;
}else{
i++;
}
}else{
break;
}
}while(true);
count++;
}
return myorder;
}
public void Print_Order(ArrayList<Order> a){ //打印指令
for ( int i = 0 ; i < a.size(); i++){
System.out.println(i+" "+a.get(i).getOrder()+" "+a.get(i).getAddress()+" "+a.get(i).isFlag());
}
}
public void Print(){ //打印所有指令
for ( int i = 0 ; i < this.page.size() ; i++){
this.page.get(i).Print();
}
}
public boolean IsALLVisited(){ //判断页面是否全部访问
boolean flag = true;
for ( int i = 0 ; i < this.page.size() ; i++){
if ( this.page.get(i).isFlag() == false){
flag = false;
break;
}
}
return flag;
}
}对于FIFO，LRU算法我们利用接口来实现，代码如下： FIFO接口如下:
package 页面调度;
public interface FIFO {
public void CarryOutFIFO(Page MyPage);
}LRU接口如下:
package 页面调度;
public interface LRU {
public void CarryOutLRU(Page MyPage);
}最后实现FIFO与LRU算法，代码如下:
package 页面调度;
import java.util.ArrayList;
public class Shdeule implements FIFO,LRU{
private int MissPage = 0; //缺页数
private double MissPageRate = 0; //缺页率
private ArrayList<Order> MemoryBlock = new ArrayList<Order>(); //内存块
private ArrayList<Order> LongNotUse = new ArrayList<Order>(); //最久未使用页面
public int getMissPage() {
return MissPage;
}
public void AddMissPage() {
MissPage++;
}
public void setMissPage(int missPage) {
MissPage = missPage;
}
public ArrayList<Order> getMemoryBlock() {
return MemoryBlock;
}
public double getMissPageRate() {
return MissPageRate;
}
public void setMissPageRate(double missPageRate) {
MissPageRate = missPageRate;
}
public int SearchAddress(int address ,ArrayList<Order> longNotUse2){ //在内存块中寻找页面
int flag = -1;
for ( int i = 0 ; i < this.MemoryBlock.size() ; i++){
if (this.MemoryBlock.get(i).getAddress() == address){
flag = i;
break;
}
}
return flag;
}
public void Print(){
System.out.println("缺页数为:"+this.getMissPage());
System.out.println("缺页率为:"+this.getMissPageRate());
}
@Override
public void CarryOutFIFO(Page MyPage) { //FIFO调度算法
// TODO Auto-generated method stub
ArrayList<Order> myorder;
boolean flag = false;
do{ //开始执行FIFO
myorder = MyPage.VisitOrderAlgorithm();
if ( myorder != null){
for ( int i = 0 ; i < myorder.size() ; i++){
int index = this.SearchAddress(myorder.get(i).getAddress(),this.getMemoryBlock());
if ( !this.IsFull()){
if ( index == -1){
this.AddMissPage();
this.MemoryBlock.add(myorder.get(i));
}
}else{
if ( index == -1){
this.AddMissPage();
this.MemoryBlock.add(myorder.get(i));
this.MemoryBlock.remove(0);
}
}
}
}
flag = MyPage.IsALLVisited();
}while (flag == false);
this.setMissPageRate(this.getMissPage() * 1.0 / MyPage.getNumber());
}
public boolean IsFull(){
boolean flag = false;
if(this.getMemoryBlock().size() == 4){
flag = true;
}
return flag;
}
@Override
public void CarryOutLRU(Page MyPage) { //LRU调度算法
// TODO Auto-generated method stub
ArrayList<Order> myorder;
boolean flag = false;
do{
myorder = MyPage.VisitOrderAlgorithm();
if ( myorder != null){
for ( int i = 0 ; i < myorder.size(); i++){
int index = this.SearchAddress(myorder.get(i).getAddress(), this.getMemoryBlock());
if ( !this.IsFull()){
if ( index == -1){
this.AddMissPage();
this.MemoryBlock.add(myorder.get(i));
LongNotUse.add(myorder.get(i));
}else{
Order tmp = myorder.get(i);
int tmp_index = this.SearchAddress(tmp.getAddress(), LongNotUse);
if ( tmp_index != -1){
LongNotUse.add(tmp);
}
}
}else{
Order tmp;
if ( index == -1){
tmp = this.LongNotUse.get(0);
int tmp_index = this.SearchAddress(tmp.getAddress(),this.MemoryBlock);
if ( tmp_index != -1){
this.getMemoryBlock().remove(tmp_index);
this.getMemoryBlock().add(tmp_index,myorder.get(i));
this.AddMissPage();
LongNotUse.remove(0);
LongNotUse.add(myorder.get(i));
}
}else{
tmp = myorder.get(i);
int tmp_index = this.SearchAddress(tmp.getAddress(), LongNotUse);
LongNotUse.remove(tmp_index);
LongNotUse.add(myorder.get(i));
}
}
}
flag = MyPage.IsALLVisited();
}
}while(flag == false);
this.setMissPageRate(this.getMissPage() * 1.0 / MyPage.getNumber());
}
public void CarryOut(Page MyPage){
System.out.println("------------------------------------开始FIFO-------------------------------");
this.CarryOutFIFO(MyPage);
this.Print();
System.out.println("------------------------------------结束FIFO-------------------------------");
for (int i = 0 ; i < MyPage.getNumber() ; i++){
MyPage.getPage().get(i).setFlag(false); //把所有指令标志位清零
}
this.getMemoryBlock().clear(); //把内存块清零
this.setMissPage(0); //把缺页数清零
System.out.println("------------------------------------开始LRU--------------------------------");
this.CarryOutLRU(MyPage);
this.Print();
System.out.println("------------------------------------结束LRU--------------------------------");
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Page MyPage = new Page(320);
Shdeule myshdeule = new Shdeule();
myshdeule.CarryOut(MyPage);
}
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